Observations of a cavitation bubble interacting with a solid boundary as seen from below

We present a schlieren photographic sequence of a laser generated cavity in water interacting with a solid boundary as seen from the boundary's perspective looking through the bubble. Previous studies have photographed the collapsing bubble from the side and it is unclear from these photographs once a bubble becomes toroidal how the central hole develops. Our schlieren sequence displays the jet first penetrating the lower bubble surface and then follows the evolution of the central channel as the bubble contracts and reexpands. It is felt that the bubble shapes recorded add further knowledge to the possible damage mechanisms of cavitation.